Dopant regions within a semiconductor body are required in all semiconductor components. Dopant regions which extend deep into the semiconductor body or are situated deep in the semiconductor body are required for some applications. A field stop zone of an IGBT (insulated gate bipolar transistor) or of a diode serves as an example of this. The production of such a field stop zone, i.e. of a zone of increased doping deep in the semiconductor body, is described, for example, in DE 10 2004 047 749 A1.
A field stop zone is usually produced by diffusion, particularly in the case of semiconductor wafers having a relatively small diameter(≦6 inches) or thicknesses of above 200 μm. In this case, by way of example, for the production of an n-type dopant region as a field stop zone, either phosphorus or selenium atoms are indiffused into the semiconductor body. This usually results in doping profiles having a Gaussian distribution and a penetration depth into the semiconductor body of typically between 1 μm and 30 μm.
Field stop zones, which have to be produced at relatively low temperatures on account of the semiconductor wafer thickness and the wafer diameter, are usually produced by proton implantation. In this case, temperatures in the range of 400° C. are usually sufficient for producing the desired n-doped field stop zones. What is disadvantageous in this case, however, is that the resulting doping profile of the field stop zone has a considerable undulation. This can lead e.g. to an undesirable change in the gradient in the current and voltage profile during the turn-off operation of e.g. an IGBT. However, the undulation of the doping profile can in some cases adversely affect the softness of the turn-off operation.